Adaptive heat flow calorimeter

ABSTRACT

Apparatus and methods are provided for providing flexible and repairable testing capabilities for systems that generate or absorb heat such as energy storage systems. One embodiment can include a temperature bath structure adapted to contain and maintain a fluid bath at a predetermined temperature, an outer containment structure adapted to insert into the temperature bath structure, heat sinks, thermal sensor assemblies, and an internal containment structure where the thermal sensor assemblies and heat sinks removably attach to different sections of the inner containment structure so as to measure heat flow into or out of the inner containment structure&#39;s different sections. Embodiments of the invention enable rapid insertion/removal of samples as well as replacement of sections of the system including embodiments or parts of thermal sensor assemblies as well as enabling separate thermal measurements associated with different sections of a sample under test within the inner containment structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of and claims priority to U.S.patent application Ser. No. 14/539,241, filed on Nov. 12, 2014, entitled“ADAPTIVE HEATH FLOW CALORIMETER”, which claims priority to U.S.Provisional Patent Application Ser. No. 62/035,738, filed Aug. 11, 2014,entitled “ADAPTIVE HEAT FLOW CALORIMETER,” the disclosures of which areexpressly incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein was made in the performance of officialduties by employees of the Department of the Navy and may bemanufactured, used and licensed by or for the United States Governmentfor any governmental purpose without payment of any royalties thereon.This invention (Navy Case 200,416) is assigned to the United StatesGovernment and is available for licensing for commercial purposes.Licensing and technical inquiries may be directed to the TechnologyTransfer Office, Naval Surface Warfare Center Crane, email:Cran_CTO@navy.mil.

BACKGROUND AND SUMMARY OF THE INVENTION

Efforts to obtain increased energy density of battery cells highlight aneed for electrochemical techniques as well as additionalcharacterization methods for these cells in order to meet user needs andsafety requirements. In particular, a continuing need has called forthinventive efforts for developing novel calorimeters to satisfy variousrequirements for requiring activities including high energy densitysystems such as chemical energy storage systems, propellant, explosive,and pyrotechnic devices. To support optimization of electro chemicalenergy storage systems in particular it is necessary to understand theirthermal characteristics at rest and under prescribed charge anddischarge cycles. In one example, a need existed to develop acalorimeter system able to accommodate multiple battery cellconfigurations and provide empirical system data for use in modeling andsimulation. Heat capacity, and thermal efficiency for each battery cellwere determined, as well as the actual heat load from each surface ofthe cell. The heat flow from each of six surfaces of the cell andoverall thermal efficiency were obtained with the cell at rest and undera variety of prescribed charge and discharge cycles representative oftypical usage of these cells. Testing was completed isothermally at 25°C. to capture the requirements necessary to remove the entire generatedthermal load from the battery cell. Moreover, these needs also includeda requirement to create testing systems which are capable of largertesting capabilities that necessarily includes a need to use largersystems, create more testing options with respect to samples under test,and create an ability to more cost effectively repair or replace costlycomponents in such test systems which existing systems do notaccommodate in a cost or time effective manner. As systems are scaled upin size, there is a higher level of failures in system components whichrequire new designs to accommodate repairs or maintenance rather thanthrowing out large sub-assemblies. Also, there is a need to be able toswap out components for greater customized design or configurability oftesting systems with respect to desired testing processes or datacollection.

As an example of one embodiment, an improved measuring cell for atemperature bath was designed and constructed to measure the heat flowof larger cells (e.g., 18×8×16 cm). Heat flows from 0.01 to 7.00 Wattswere measured with an average signal noise less than 1 mW. In oneexample, heat capacities of samples were also determined withexperimental deviation of less than 2%.

Embodiments of the invention can include apparatus and methods forproviding flexible and repairable testing capabilities for systems thatgenerate or absorb heat such as energy storage systems. One embodimentcan include a temperature bath structure adapted to contain and maintaina fluid bath at a predetermined temperature, an outer containmentstructure adapted to insert into the temperature bath structure, heatsinks, thermal sensor assemblies, an internal containment structure, andthermal barriers between different elements of the invention to isolatedifferent sections from each other. An embodiment of the invention caninclude a system where the thermal sensor assemblies and heat sinksremovably attach to different sections of the inner containmentstructure so as to measure heat flow into or out of the innercontainment structure's different sections without being altered bydirect thermal contact with other inner containment sections.Embodiments of the invention permits rapid insertion/removal of samplesas well as replacement of sections of an exemplary system includingembodiments or parts of the thermal sensor assemblies as well asproviding an ability to obtain separate thermal measurements associatedwith different sections of a sample under test within the innercontainment structure. Other aspects of the invention include acapability to insert or substitute existing components such ascontainment structure elements, thermal sensors etc. with differentsized elements or structures to accommodate different types of samplesor differently sized samples under test. Embodiments can includeelectrical bus or wiring structures such as separate wiring sections andquick disconnects that also permit rapid repairs or alteration ofconfigurations of various aspects of embodiments of the invention.

Additional features and advantages of the present invention will becomeapparent to those skilled in the art upon consideration of the followingdetailed description of the illustrative embodiment exemplifying thebest mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of the drawings particularly refers to theaccompanying figures in which:

FIG. 1 shows an exemplary calorimetric system being removed from aprecision temperature bath in accordance with one embodiment of theinvention;

FIG. 2 shows a simplified perspective view of a battery cell under testinside an exemplary calorimetric measuring unit installed in a precisiontemperature bath in accordance with one embodiment of the invention;

FIG. 3 shows positioning of an exemplary calorimetric measuring unit inan exemplary fluid bath in accordance with one embodiment of theinvention;

FIG. 4 shows a calorimetric measuring unit of an exemplary calorimetricmeasuring unit with a heat sink removed in relation to an exemplaryembodiment of the invention;

FIG. 5 shows an exemplary embodiment of an exemplary calorimetricmeasuring unit of an exemplary calorimetric measuring system with a topheat sink removed in accordance with one embodiment of the invention;

FIG. 6 shows a top view of a corner of an exemplary inner containmentstructure of a calorimetric measuring unit in relation to an exemplaryembodiment of the invention;

FIG. 7 shows an exemplary inner containment structure with thermalisolation barriers in relation to an exemplary embodiment of theinvention;

FIG. 8 shows a cross sectional diagram with top and bottom units removedin relation to an exemplary embodiment of the invention;

FIG. 9 shows an exemplary thermal sensor assembly used in an exemplarycalorimetric measurement unit in accordance with an exemplary embodimentof the invention;

FIG. 10 shows an exemplary thermal sensor assembly attached to an innercontainment structure of a calorimetric measuring unit in accordancewith an exemplary embodiment of the invention;

FIG. 11 shows an exemplary orientation of a wiring system forthermopiles with respect to an inner containment structure in accordancewith an exemplary embodiment of the invention;

FIG. 12 shows exemplary data signal wires from an exemplary thermalsensor assembly terminating in a quick release electrical connector inaccordance with an exemplary embodiment of the invention;

FIG. 13 shows a flow chart depicting an exemplary simplified method ofrepair for a calorimetric measuring unit in relation to an embodiment ofthe invention;

FIG. 14 shows a flow chart depicting an exemplary method of use for acalorimetric measuring unit in relation to an embodiment of theinvention;

FIG. 15 shows a flow chart depicting an exemplary method of manufacturefor a calorimetric measuring unit in relation to an embodiment of theinvention;

FIG. 16 shows a flow chart depicting an exemplary method of manufacturefor a sensor assembly in relation to an embodiment of the invention;

FIG. 17 shows exemplary heat flow curves showing individual signals foreach surface of a sample cell from different sensor assemblies as wellas the combined heat flow, which is the curve of largest value.

DETAILED DESCRIPTION OF THE DRAWINGS

The embodiments of the invention described herein are not intended to beexhaustive or to limit the invention to precise forms disclosed. Rather,the embodiments selected for description have been chosen to enable oneskilled in the art to practice the invention.

Generally, one exemplary embodiment of an improved calorimeter testsystem was designed to accept two different sizes of silver zinc basedbattery cells. The exemplary cells under test provided access to theirnormal electrical test system through a use of extended charging cables.An exemplary calorimeter test system was designed to approximateoperational conditions in which the test cell is operated isothermallyat 25° C. Maintaining an isothermal operating environment can beachieved through the use of a precision temperature bath. One exemplarytest system can be designed such that each of six surfaces of the testcell (cuboid sample) can be provided a thermal conduction pathway ofleast resistance that can be isolated from the other five surfaces andchanneled through a plurality of thermopiles. In this example, exemplarythermopiles function according to the Seebeck effect and generate avoltage corresponding to a temperature difference on either side of theprecision measurement device. A plurality of thermoelectric junctions ineach thermopile amplifies this effect and thus lowers a minimumtemperature difference required to generate a voltage to nearlyisothermal values.

FIG. 1 shows maneuverability of an exemplary embodiment of acalorimetric measuring unit assembly 1. A user simply grasps handle 11attached to a lid 13 in an outer containment structure 19 and pullsoutwardly to extract outer containment structure 19 from fluid bath 9(not shown in FIG. 1).

FIG. 2 shows a simplified diagram of a tested sample 3 inside anexemplary calorimetric measuring system 1 installed in an exemplaryprecision temperature measurement bath 9. In one embodiment, a sample 3can be a battery. Exemplary sensor assembly 5 can be seen between anexemplary inner containment structure 15 which includes innercontainment structure sections, e.g., section 14″″″ (e.g. a top side)(see FIGS. 2 and 3 for more exemplary details), holding the sample 3 andheat sink 7′. In one embodiment a thermal isolation barrier 17 (shownin, e.g., FIGS. 5 and 6) can be located between edges of innercontainment structure 15 and edges of each sensor assembly 5. Thermalisolation barriers 17 span a portion along edge sections of innercontainment structure 15 and are provided to thermally isolate each wallof inner containment structure 15 from other adjacent walls to avoidunmeasured thermal contributions to each sensor assembly 5 thermallycoupled to its respective wall of the inner containment structure 15(e.g., thermal cross talk or undesired thermal energy migration betweenwalls or segments associated with different thermocouples orthermopiles). Exemplary aspects of an embodiment of the invention asdescribed herein allows for calorimetric measuring system 1 to measureheat flow from each side of sample 3 independent of other sides.

In one embodiment, side, top, and bottom assemblies inside of outercontainment structure 19 can include thermal isolation barriers sections17, sensor assembly 5, and heat sink 7′ where each applicable assemblyis respectively coupled to each side, top, and bottom of the innercontainment structure 15. Heat sinks 7, 7′, etc. can be large enoughwith a high enough heat capacity such that thermal energy releasedthrough any sample's face is absorbed into heat sinks 7, 7′, etc.However, thermal energy released from sample 3 and through elements ofcalorimetric measuring unit 16 is not enough to change the temperatureof the heat sinks. Thermal energy absorbed by heat sinks 7, 7′, etc.then dissipates through outer containment structure 19 and into athermally stable fluid bath 9. Exemplary aspects of this invention asdescribed herein also allows for calorimetric measuring unit 1 to havean increased capacity for samples that are larger and have higher heatload capacities. A high capacity of heat sink 7 also helps to maintainan isothermal operating environment.

In one exemplary embodiment, each of heat sinks 7, 7′, 7″, etc. areconnected with respective surfaces of inner containment structure 15with thermally non-conductive bolts (not shown) similar to the one 33shown in FIG. 5 on the top heat sink. An embodiment can also include alifting eye bolt 35 which aids in positioning the inner containmentstructure 15 inside the outer containment structure 19 for operation.

Referring back to FIG. 2, an embodiment can include cables (not shown)that connect to sample 3 which permit operation of a sample e.g.,battery which permit calorimetric testing of a sample under operationaltest or use configurations. These cables can carry charge from acharging system (not shown) to sample 3 when testing and generating datafor sample 3 in the calorimetric measuring unit 16. The exemplarymeasuring system 1 can also have a handle 11 for removal of outercontainment structure 19, and lid 13 enclosing outer containmentstructure 19. The lid 13 can be removably attached to the outercontainment structure to permit the lid to be opened and closed afterremoval or insertion into the calorimetric measuring unit 1.

An example of positioning of an exemplary calorimetric measuring cell inthe fluid bath can be seen more clearly in FIG. 3. FIG. 3 shows aperspective cut-away view of the exemplary assembly shown in FIG. 2 butit also shows a stirrer 37 operable to mix the fluid bath in apredetermined manner to further control a temperature of fluid bath 9.

In one exemplary embodiment of calorimetric measuring system 1, atemperature control mechanism in fluid bath 9 can be provided. Exemplarytemperature control mechanism can comprise an integrated heater (notshown) in a bottom plate of the fluid bath 9 and a cooling element (notshown) inserted into fluid bath 9 adapted to serve as an adjustable heatexchanger for fluid bath 9 located at a top portion of fluid bath 9.Heating or cooling elements can also be placed onto different locationsof said fluid bath.

Referring to FIG. 4, each exemplary heat sink 7, 7′, etc., can berespectively thermally coupled to a different respective surface orsection of inner containment structure 15 by non-heat conductive bolts(not shown) that insert into recessed apertures 36 of the heat sinks inone embodiment. FIG. 4 also shows an outer thermally conductive surface21A′ of thermal sensor assembly 5 which is positioned to thermallycouple with adjacent structures (e.g., inner containment structure 15 orheat sinks, e.g., 7), as well as wires 31 attached to thermal sensors inthermal sensor assembly 5. In this example, wires 31 carry electricalsignals corresponding to measurement values from thermopiles for eachside (23A, 23B, etc.) of the inner containment structure 15 to a dataacquisition device 25 (not show in FIG. 4 but, e.g., shown in FIGS. 8and 11).

FIGS. 5, 6, and 7 show thermal isolation barriers 17 used in relation toembodiments of the invention. Thermal isolation barriers are used insome embodiments to isolate thermal sensor assemblies from edge sectionsof adjacent sides of the inner containment structure 15. As shown inFIG. 6, a thermal isolation barrier 17 is disposed between one sensorassembly 5 and an adjacent inner containment structure section 14″(e.g., a side) that is parallel and adjacent to an inner containmentstructure section 14′ that is parallel and in contact with the body ofthermal sensor assembly 5. A different thermal isolation barrier 18 isdisposed between inner containment structure section 14′ and adjacentinner containment structure 14′ that is, in this embodiment, an end sideof the inner containment structure 15 forming two sides of the innercontainment structure 15. Thermal isolation barriers, e.g., 17, insertedbetween edges of adjacent sections such as inner containment structuresections and thermal isolation barriers serves to ensure that heat datafor each side of sample 3 can be measured independently from the othersides to avoid unmeasured thermal contributions to any thermal sensorassembly that are not oriented towards a face of inner containmentstructure 15. For example, when sample 3 is charged, heat data can begenerated for each side of sample 3 facing a thermally isolated sectionor side of the inner containment structure independent of the othersection or sides. If no thermal isolation barriers, e.g., 17, are used,then calorimetric measuring unit 1 would generate only one measurementfor the total heat flow generated by sample 3. Embodiments can alsoinclude non-thermally conductive contact between outer surface (e.g.,21) of each sensor assembly, e.g., 5, and thermal isolation barriers,e.g., 17; such contact would not allow for individualized andindependent heat data measurements for each thermally isolated sectionof inner containment structure 15.

In one exemplary embodiment, one or more thermal isolation barriers,e.g., 17, can comprise a gasket made of a small silicone sheet that islocated between sensor assembly 5 and inner containment structure 15. Inanother exemplary embodiment, one or more thermal isolation barriers,e.g., 17, can comprise a thermal isolation strip made of clearpolycarbonate located between sides of inner containment structure 15.

FIGS. 6 and 7 shows another type of thermal isolation barrier 18positioned with respect to different components as the previouslydiscussed thermal isolation barriers, e.g., 17. As shown in FIGS. 6 and7, thermal isolation barriers 18, 18′ can be positioned between innercontainment structure sections 14, 14′ (e.g., sides). Likewise,additional thermal isolation barriers can be inserted between each innercontainment structure section and each adjacent inner containmentstructure section to thermally isolate each inner containment structuresection (e.g., side walls as well as floors and top section) from eachother section. Thermal isolation barriers 18, 18′, etc. operate inconjunction with thermal isolation barrier 17, 17′, etc. to create anisothermal environment and to ensure that the heat data for each side ofsample 3 can be measured independently from the other sections (e.g.,sides) of the inner containment structure 15.

FIG. 8 shows a partial cross-sectional top view of exemplarycalorimetric measuring unit 1 excluding top and bottom portions (eachhaving thermal sensor assemblies and heat sinks along with thermalisolation barriers isolating them from side sections of the innercontainment structure 15) as well as two of four side thermal sensorassemblies 5′, 5″ and heat sinks 7′, 7″. Exemplary inner containmentstructure 15 is shown with a sample 3 inside it. Thermal isolationbarriers 17, 17′, 17″, and 17″′ are disposed adjacent to outer edges ofinner containment structure 15 sides. Another set of thermal isolationbarriers 18, 18′, 18″, 18″′ are disposed between sides of innercontainment structure 14, 14′, 14″, 14″′. Edge sections of thermalsensor assemblies e.g., 5, 5″′, are disposed adjacent to thermalisolation barriers 17, 17′ and 17″, 17″' respectively. Heat sinks 7 and7″′ are adjacent to sensor assemblies 5, 5″′ respectively and outercontainment structure 19 (not shown).

FIGS. 8 and 9 show components of sensor assembly 5. Assembly 5 comprisesof two thermally conductive surfaces 21A and 21A′ and a plurality ofthermopiles 23A, 23A′, etc. between them which conduct heat between thetwo surfaces 21A, 21A′. Thermopiles 23A, 23A′ measure the heat flow asit passes through them and sends that measurement value to a dataacquisition system 25 (shown in FIG. 8). A thermal sensor assembly,e.g., 5, is provided for each side, top, and bottom of the innercontainment structure 15. This allows for individualized, independentmeasurements for each side of sample 3 facing a thermally isolatedmeasuring section of the inner containment structure 15.

Referring back to FIG. 8, when sample 3 inside the inner containmentstructure 15, generates heat, such as a during a charge cycle. The heatflow moves from sample 3 to the adjacent sensor assembly 5. Withinsensor assembly 5, heat flows through thermally conductive surface 21,thermopiles 23A, 23A′, etc., and a second thermally conductive surface21A′. As heat moves from thermopiles 23A, 23A′, etc. to a secondthermally conductive surface 21, a measurement value is sent fromthermopiles 23 to a connected data acquisition system 25. Dataacquisition system 24 is connected to the plurality of thermopiles 23A,23A′, etc. through a set of separate wires 31 for each sensory assembly5 as shown in FIGS. 11 and 12 which in turn is connected to a processingsystem 27 and an output system 29. In one embodiment, the thermopilesare arranged as such to be thermally in parallel but electrically inseries. Such a mechanism for heat flow is present for each side innercontainment structure 15 as heat would flow through the side'sthermopiles generating a measurement value for data acquisition system24. When sample 3 consumes thermal energy for a process the heat flowreverses direction in such that heat from the bath flows back throughthe system and into the system resulting in an opposing measurement.

From data acquisition system 24, a measurement value then is sent to aconnected processing system 27. In an exemplary embodiment, processingsystem 27 contains a GPIB/Ethernet input/output section and has aprocessor and a storage medium box within the overall processing systembox. From there, the measurement value is sent to an output device 29which displays or outputs the information. In another exemplaryembodiment, the output device can be a printer or a display.Measurements for each sensory assembly 5 can be done separately for eachinner containment structure 15 facing different sides of sample 3.

In an exemplary embodiment shown in FIG. 9, sensor assembly 5 has twothermally conductive surfaces 21A, 21A′ that are held together by anon-heat conductive bolt 33.

FIG. 10 shows an exemplary thermal sensor assembly 5 attached to aninner containment structure 15. Sensor assembly 5 has thermallyconductive surfaces 21A, 21A′ that are held together by a non-heatconductive bolt 33. Spacer 24 is made from a non-conductive material andoperates, in this embodiment, to prevent the thermopiles in thermalsensor assembly 5 from becoming damaged by a force applied to either ofthe thermally conductive surfaces 21A, 21A′.

As shown in FIG. 11, a non-heat conductive bolt(s) (not shown) goesthrough the thermally conductive surfaces at recessed feature 36 in heatsinks (e.g., 7, 7′, etc.) and attaches to inner containment structure 15through thermal sensor assembly 5. There is also spacer 24 in anotherexemplary embodiment. Spacer 24 is made from a non-conductive materialand operates to prevent the thermopiles from becoming damaged by a forceapplied to either of the thermally conductive surfaces 21A, 21A′.

In an exemplary embodiment, the wires 31 terminate in common plugs 32 asshown in FIG. 12. Plugs 32 allow for greater ease of use with the dataacquisition system 25 as the user can quickly disconnect the system bypulling plugs at the calorimetric measuring unit rather than splicingwires as in prior systems.

Referring to FIG. 13, a method of repair of a system in accordance withan embodiment of the invention is shown that can include providing anassembly comprising a calorimetric measuring system 1, e.g. FIGS. 2 and3, such as described herein at step 101. At step 102, when it isdetermined by the user that thermopiles 23 need to be replaced, removeouter cover from outer containment 19. At step 107 remove innercontainment structure 15 from outer containment structure 19. Forexample, step 107 can be accomplished by a use of lifting eye bolt 35(e.g., shown in FIGS. 2, 3, 4). Next, according to step 109, heat sink7′ is detached from inner containment structure 15 and sensor assembly 5by the removal of non-heat conductive bolt(s) at recessed areas 36.Replace thermal sensor assembly 5 with a spare assembly as in step 111.Next, process continues by sending a faulty unit, e.g., thermal sensorassembly 5, back to the repair facility for step 113 and proceeding tostep 117 for in field repairs. At step 113, outer heat sink wall section21A′ is detached from the sensor assembly 5 with the removal of at leastone non-heat conductive bolt 33. At step 113 a damaged thermopile(s) 23a can be extracted from inner heat sink wall section 21 and newfunctional thermopile 23 b inserted into sensor assembly 5. At step 117,heat sink 7 is reattached to sensor assembly 5 and inner containmentstructure 15 and by the reinsertion of non-heat conductive bolts atrecessed areas 36. At step 119, inner containment structure 15 isreinserted into outer containment structure 19. Proceeding to step 120,replace the outer cover over the outer containment 19. Operation ofcalorimetric measuring system 1 can resume at step 23.

Referring to FIG. 14, a method of use of a system in accordance with anembodiment of the invention can include providing a sample 3 for testingat step 201. Sample 3 is then inserted within inner containmentstructure 15 at step 203. Then, at step 205, a top section of innercontainment structure 15 is coupled to the walls of inner containmentstructure 15. At step 206, providing and coupling thermal isolationbarriers 17, 17′, etc.; sensor assemblies 5, 5′, etc.; and heat sink 7,7′, etc. for each respective side, top and bottom of inner containmentstructure 15 is accomplished (see, e.g. FIGS. 4, 5, and 8). Note thatstep 206 in this embodiment is performed prior to sample insertion; ifno maintenance is required, this step does not need to be modified foreach sample. Inner containment structure 15 is placed inside outercontainment structure 19 according to step 207. Note with respect tostep 207, in this embodiment structure 15 with heat sinks generallystays inside structure 19 during changing of samples but are removableif necessary for a sample to be removed or inserted but such removal notrequired. At step 209, a top section of inner containment structure 15is coupled to outer containment structure 19. At step 213, sample 3 isallowed to charge or discharge. At step 215, a charge is applied tosample 3, and at step 217, heat flow from sample 3 through each side ofinner containment structure 15 is measured and recorded independently ofthe other sides of inner containment structure 15. Steps 213 to 215 canbe omitted if sample 3 does not require a charge, such as with othersample types besides electrochemical energy storage devices. Charge anddischarge profiles are sample dependent. The number of charges anddischarges is variable from zero to any number as directed by thesample. The charge and discharge rates can also be variable or constantas required by the sample. Typically a charge and discharge program canbe an established protocol that is normally completed without theaddition calorimetry, such as lot acceptance testing.

Referring to FIG. 15, a method of manufacture of a system in accordancewith an embodiment of the invention is shown that can include providingan outer containment structure 19 such as described herein at step 301.At step 303, an inner containment structure 15 is provided as well. Atstep 304, thermal isolation barriers 17, 17′, etc. are attached on anouter surface of inner containment structure 15, e.g. FIGS. 5 and 6. Atstep 305, a sensor assembly 5, 5′, 5″, etc. and a heat sink 7, 7′, etc.is attached to each respective side of inner containment structure 15with non-heat conductive bolt at recessed areas 36. At step 306, steps304 and 305 are repeated such that thermal isolation barriers 17′, 17″,etc. and sensor assemblies 5′, 5″ are attached to each respective outersurfaces of inner containment structure 15. At step 307, innercontainment structure 15 with thermal isolation barriers 17, 17′, etc.;sensor assemblies 5, 5′, etc.; and heat sinks 7, 7′, etc. is placedinside outer containment structure 19 to form calorimetric measuringunit 1. Finally, at step 309, calorimetric measuring unit 1 is placedinside fluid bath 9. Note that step 309 can be moved to, e.g., initialsetup, and thus leave the calorimetric measuring unit 1 inside the fluidbath for test operations and thus skip step 309 at this point of thisexemplary process.

Referring to FIG. 16, an exemplary method of manufacture of a sensorassembly in accordance with an embodiment of the invention can includeproviding a first heat sink wall section 21A at step 305A. At step 305B,a plurality of thermopiles 23A, 23A′, etc. are attached to first heatsink wall section 21A. In one embodiment, thermopiles 23A, 23A′, etc.are adhered to first heat sink wall section 21A with a thermallyconductive paste, improving thermal contact and providing a weakadhesive bond. At step 305C, a second heat sink wall section 21A′adjacent to the thermopiles 23A, 23A′, etc. and first heat sink wallsection 21A. At step 305D, second heat sink wall section 21A′ isattached to first heat sink wall section 21A with thermopiles 23A, 23A′,etc. between the two surfaces. The heat sink wall sections 21 aresecured to each other using non-heat conducting fasteners 33, such asPEEK bolts. At step 305E, steps 305A-305D are repeated for assemblingsensor assemblies 5′, 5″, etc. for each side of inner containmentstructure 15.

An exemplary calibration of the test system can be achieved throughJoule heating. In one example, thermal conduction pathways also containprecision resistors or resistive heaters at fixed locations that areused to calibrate the thermopiles in that pathway by producing a knownheat flow as calculated using Ohm's law. To ensure any “leakage” intounintended pathways is accounted for, each conduction pathway can becalibrated individually. Finally, one embodiment can include a pointsource placed in the approximate center of the test chamber and allowedto radiate thermal energy on to the collection surfaces of all of thepathways at the same time. The sum value is validated based on thecalculated value of the point source. One exemplary calorimeter systemconstant was determined using silicon glass tubes filled with siliconglass beads as a known standard.

In one example, two silver-zinc cells were selected for calorimetrytesting. A first can be designated Cell A with a weight of 4.32 kg whenfilled with electrolyte. A second cell can be designated Cell B with afilled weight of 4.11 kg. Heat capacity value for the exemplary sampleswas determined by changing the calorimeter bath temperature by 10° C.and then measuring the amount of energy absorbed into the test chamberin order to raise the cell to the new temperature and back intoequilibrium with the calorimeter bath. This exemplary process was thenrepeated by lowering the calorimeter bath temperature to the original25° C. Raising and lowering of the bath temperature was repeated againto provide a total of four separate heat flows to use in specific heatcalculations.

In another example, once a heat capacity of the sample cell wasdetermined, an exemplary cell was connected to the electrical testsystem and cycled according to the normal test plan for these cells.Both cells can be cycled at constant charge and discharge rates,including 10, 25, and 35 amps, inside the calorimeter. For each cycle,several plots, such as those shown in FIG. 18, can be generatedincluding heat flow vs. time with an overlay of the voltage data, anormalized plot in which heat flow per surface area is compared for eachsurface of the sample cell (the top surface is inherently skewed low dueto the measurement cell design), and heat flow vs. ampere hour plot forthe discharge and charge steps.

Exemplary heat flow curves, e.g. FIG. 17, provide the individual signalsfor each surface of the sample cell as well as the combined heat flow,which is the curve of largest value. The start time for each time plothas been normalized to the start of the discharge step. The electricalcycling program was a discharge, rest, charge, and final rest. However,due to the transfer time required for the heat to move from the samplecell and across the measuring pathway the total thermal transfer time islonger than the time required for the individual electrical charge ordischarge.

In an example, an average heat generated is calculated by integratingthe area under a heat flow curve and then dividing by the time requiredfor the electrical discharge, and not the longer time of total heattransfer.

In one example, charge or discharge number is the number in thecalorimeter. Both sample cells in this example can be previously subjectto normal lot acceptance testing prior to testing in the calorimeter. Aninteresting feature of an exemplary heat flow curve can be shown duringa charging step. An endothermic portion can be observed at a start ofeach charging step.

Calorimetric data obtained during charge and discharge cycles was alsoused to determine the thermal efficiency of the sample cells. Totalelectrical energy for each charge or discharge was divided by the sum ofthe electrical energy and thermal energy.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe spirit and scope of the invention as described and defined in thefollowing claims.

1.-8. (canceled)
 9. A method of using a thermal energy testing systemcomprising: providing a sample for testing; providing an innercontainment structure of a calorimeter comprising a plurality of wallsections including side sections, a selectively removal top section, anda bottom section, wherein said inner containment structure furthercomprises attaching a plurality of thermal isolation barriers disposedbetween each of said sections to thermally isolate each section from alladjacent sections as well as additional thermal isolation barriersdisposed on outer surfaces of said inner containment structure;inserting a sample into said inner containment structure; removablycoupling said top section of said inner containment structure torespective side sections of adjacent walls of said inner containmentstructure; providing a plurality of thermal sensor assemblies andrespectively coupling each of said thermal sensor assemblies to saidouter surfaces of said inner containment structure so said sensorassemblies can be removed and replaced, wherein said sensor assembliesare physically separated from adjacent edges of other sensors inproximity to each other so as to prevent thermal energy fromtransferring between said sensor assemblies by direct physical contactwith each other; removably attaching ones of a plurality of heat sink torespective said outer surfaces of said inner containment structure;inserting inner containment structure with said sample into an outercontainment structure; coupling said top section of inner containmentstructure to said outer containment structure; inserting said outercontainment structure into a fluid bath; allowing said sample todischarge; and measuring and recording a heat flow data through eachside of said inner containment structure independently of other sides ofsaid inner containment structure.
 10. The method of claim 9 wherein saidsample comprises an electrical energy structure that is charged ordischarged at a controlled rate or said sample comprises other materialssuch as propellants or pyrotechnics that decompose upon heating.
 11. Themethod of claim 9 further comprising a heat flow generated by thestimulated charge, stimulated discharge, or self-discharge of saidsample applying a charge to said sample to generate a heat flow.
 12. Themethod of claim 9 wherein said sample is charged at a constant chargerate.
 13. The method of claim 9 wherein the measuring and recording stepfurther comprises: sending said heat flow data to a data acquisitiondevice; sending said data from said data acquisition device to aprocessing system; and importing said data to an input output device.14. The method of claim 9 further comprising measuring the heat capacityof said sample.
 15. The method of claim 14 wherein measuring the heatcapacity of said sample further comprises increasing said temperature ofsaid calibration bath; and measuring the amount of energy absorbed intothe test chamber to raise said sample to a new temperature that is inequilibrium with said calibration bath.
 16. The method of claim 13wherein said data is sent through a plurality of wires wherein saidplurality of wires terminates in a common plug.
 17. The method of claim9 wherein said attaching steps associated with said inner containmentstructure and said thermal sensors are repeated for each said outersurface of said inner containment structure.
 18. A method of manufacturecomprising: providing an outer containment structure; providing an innercontainment structure comprising a plurality of sections comprising sidesections, a top section, and a bottom section, said inner containmentstructure further comprises thermal isolation barriers adapted tothermally isolate each side section from each other; positioning eachone of a plurality of thermal sensor assemblies respectively in contactwith an outer surface of each of said plurality of inner containmentstructure so as to separately determine heat measurements with respectto each said sections, wherein said thermal sensors comprise at leastone thermopile, wherein each thermal sensor assembly has a separatesignal output from all other thermal sensor assemblies; removablyattaching each one of a plurality of heat sinks respectively to each oneof said plurality of thermal sensor assemblies and each section of saidsections by inserting at least one of a plurality of non-heat conductingfasteners through each one of said heat sinks, each one of saidplurality of thermal sensor assemblies into separate sections of saidinner containment structure, wherein said heat sink is also in contactwith said outer containment structure; placing said inner containmentstructure into said outer containment structure; and coupling each ofsaid signal outputs of said plurality of thermal sensor assemblies'signal outputs with a signal processing system comprising a sectionoperable to receive signals from said separate thermal sensor assembliesand determine said heat measurements.
 19. The method of claim 18 furthercomprising inserting a sample having materials which generate or consumeheat in said inner containment structure.
 20. The method of claim 18further comprising placing said outer containment structure in acalibration bath structure with a thermal conductive fluid inside saidcalibration bath structure.
 21. The method of claim 19 furthercomprising attaching a plurality of cables through an aperture in saidinner containment structure from said sample to a charging system. 22.The method of claim 18 where said attaching step further comprises usinga non-heat conductive bolt to attach said thermal sensor assembliesrespectively to said inner containment structure sections.
 23. Themethod of claim 18 where the attachment steps are repeated for each saidouter surface of said inner containment structure.
 24. The method ofclaim 18 wherein said thermal sensor assembly comprises: a first heatsink wall section; a plurality of thermopiles coupled to said first heatsink wall section; and a second heat sink wall section coupled to saidplurality of thermopiles wherein said first heat sink wall section andsaid second heat wall section have said plurality of thermopilesdisposed there between.
 25. The method of claim 24 wherein each wall,top, and bottom of said inner containment structure comprises a separatesaid thermal sensor assembly.
 26. The method of claim 24 wherein saidthermal sensor assembly further comprises a first heat sink wall sectionand second heat sink wall section disposed on opposing sides of saidthermal sensor assembly, wherein said method further comprises providinga non-thermally conductive fastener to couple said first heat sink wallsection and said second heat sink wall section with said thermal sensorassembly a respective inner containment structure section.
 27. Themethod of claim 24 further comprising: attaching a plurality of wires tosaid plurality of thermopiles; connecting said plurality of wires to adata acquisition system; connecting said data acquisition system to aprocessing system; and connecting said processing system to an inputoutput device.
 28. A method of repairing a thermal testing systemcomprising: providing a calorimetric measuring unit; removing an innercontainment structure with a plurality of thermal sensors and aplurality of heat sinks respectively each disposed on an opposing sideof said thermal sensor so as to dispose one of said thermal sensorsbetween each one of said heat sinks and a wall section of said innercontainment structure from said outer containment structure; detachingat least one said heat sink attached to said thermal sensor assembly andsaid inner containment structure; detaching said thermal sensor assemblycomprising a first and second heat sink wall section with a thermalsensor disposed there between; extracting a damaged thermopile from saidthermal sensor assembly; inserting a functioning thermopile into saidthermal sensor assembly; reattaching said thermal sensor assembly tosaid first heat sink in proximity and thermal contact with said firstheat sink wall section; reattaching said heat sink wall section and saidthermal sensor assembly to said inner containment structure so as saidsecond heat sink wall section is in thermal contact with said innercontainment structure; reinserting said inner containment structure intosaid outer containment structure; reinserting said outer containmentstructure into said fluid bath; and resuming operation of saidcalorimetric measuring unit.
 29. The method of claim 28 where saidreattaching steps relative to said inner containment structure, saidthermal sensor assembly, and said heat sink further comprise using anon-heat conductive fastener to couple said inner containment structure,said thermal sensor assembly and said inner containment structuretogether.
 30. The method of claim 28 where said detaching steps furthercomprise removing a non-heat conductive fastener to decouple said heatsink, said thermal sensor assembly, and said inner containment structurefrom each other.
 31. The method of claim 28 wherein said sensor assemblycomprises: a first and second heat sink wall section and a plurality ofthermopiles; wherein said first heat sink wall section and said secondheat sink wall section are thermally separated by said thermopiles toform a thermally conductive path from said first and second heat sinkwall sections through each said thermopiles.